Methods

Eligibility includes histologically confirmed colorectal cancer, previously received oxaliplatin-contained chemotherapy, PS: 0-1, EGFR positive and KRAS exon2 wild type. Patients (pts) received S-1 80-120 mg/day p.o. on days 1-14 and irinotecan 100mg/m2 on days 1 and 15 repeated every 28 days. Cetuximab was administrated 400mg/m2 as loading dose and continued 250mg/m2 every week or 500mg/m2 bi-weekly. The primary endpoint was response rate and the secondary endpoints were disease control rate, PFS, OS and safety. To compare with EW and BW, Fisher's exact test was used in terms of patient characteristics, AE, RR, and Log-rank test was used in terms of PFS, OS, and TTF.

Results

Between Mar 2010 and Sep 2013, 58 pts were enrolled. One patient had no treatment (57 pts were safety analysis set), and 3 pts were ineligible (54 pts were efficacy analysis set). Based on each physician choice, 34 patients of EW and 23 of BW were included in the full safety analysis set. RR was 34.4% in the EW group and 31.8% in the BW group (p = 1.000). Median PFS was 4.2 months (95% CI 3.5–4.9) in the EW group and 6.1 months (4.1-8.1) in the BW group (HR 0.752, 95% CI 0.413–1.372, p = 0.350). The most common non-hematological adverse events of grade 3 or higher were diarrhea (23.5% in the EW group vs 52.2% in the BW group: p = 0.005) and stomatitis (2.9% in the EW group vs 30.4% in the BW group: p = 0.046), these were significantly more common in the BW group.

Conclusion

IRIS/Cet appeared to be highly effective with RR and PFS in the both treatment schedule, and also had met the primary endpoint. Diarrhea and stomatitis were significantly more common in the BW group. Therefore, in case of treatment with IRIS, cetuximab should be administered weekly. The final analysis will be presented in European Cancer Congress 2015.